1. Field of the Invention
The present invention relates to microfluidic systems and devices and, more particularly, to a device for collecting blood and separating blood constituents, such as blood plasma, as a sample liquid, in which capillary forces are used and are critical in particular for the function. The present invention also relates to a method of separating blood constituents and to uses of the device for determining an intracellular parameter or for detecting one or more blood constituents.
2. Description of Related Art
A device for separating liquid components is known from EP 1 013 341 A2, which constitutes the starting point for the present invention, wherein for example blood plasma as a sample liquid is separated from the blood in a filter or a membrane and is collected by capillary forces in a collecting chamber or channel for diagnostic purposes. The channel has a substantially rectangular cross-section. It is formed in a carrier by a corresponding recess covered at the top. In addition, the channel has wedge-shaped notches as guide elements to ensure total filling of the increasing cross-section channel with the sample liquid. However, the design for the channel still does not ensure optimum filling with the sample liquid.
U.S. Pat. No. 4,906,439 and International Patent Application Publication WO 01/24931 A1 both disclose devices for separating blood plasma from blood, wherein a plurality of groove- or capillary-like individual channels are provided for collecting and carrying away the blood plasma. The disadvantage arises that the channels fill up with the sample liquid in the form of blood plasma at different rates or not at all. Accordingly, it is not possible to achieve a uniform liquid front. This is disadvantageous in terms of the diagnosis as there are no defined quantities available simultaneously or, for example, dry chemicals or the like cannot simultaneously be dissolved by the sample liquid to the desired or necessary extent.